Pulverized-fuel-burning furnace



' Nov. 5, 1929. M. FRISCH 1,734,669

PULVERIZED FUEL BURNING FURNACE Filed June 6, 1927 Patented Nov. 5, 1929 UNITED STATES PATENT OFFICE MARTIN FRISCH, OF ST. LOUIS, MISSOURI, ASSIGNOR TO INTERNATIONAL GOMBUSF TION ENGINEERING CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE rULvEarzEn-rUnL-Bunnme summon Application filed June a, 1927.- Serial No. 196,693.

This invention relates to furnaces for burning pulverized fuel.

One of the objects of the invention is to attain in pulverized fuel burnin furnaces higher combustion rates and big er capacities than are now customary.

Another object of the invention is to improve the manner of firing pulverized fuel burning furnaces whereby water wall lined combustion chambers can be used to greater advantages than heretofore.

A more specific object of the invention is to provide an improved arrangement for admitting air to pulverized fuel burning furnaees.

A further object is to reduce the loss in combustible values.

How the foregoing, together with such other objects and advantages as may hereafter appear, or are incident to the invention, are realized is illustrated in preferred form in the accompanying drawings, wherein- Fig. 1 is a sectional elevation of a boiler setting embodying the improvements, and Fig. 2 is a fragmentary sectional view illustrating a detail of the invention, the view being taken on the line 22 of Fig. 1.

Referring to the drawings the furnace comprises in general a combustion chamber A, an outlet throat B at the u per rear part thereof, and burner means G for admitting finely divided fuel into the upper art of the furnace in a downward direction a jacent the front wall a. A suitable boiler D such as the substantially horizontal tubular boiler shown is located over the outlet throat B. In this instance the walls of the combustion chamber are lined with evaporating elements comprising rows of boiler tubes 6, c and d, and a water screen E composed of a plurality of spaced tubes is provided above the ash pit F.

The pulverized fuel mixed with air is supplied to the burner means 0 by feeders 3, the air serving to transport the coal from the feeders to the burner means. The roportion of this air to the coal is in the nelghborhood of one pound of air per pound of coal; more or less being used to obtain the best ratio for properly conveying the coal to the burner means.

At the burner or burners, additional airis At the lower part of the front wall of the V furnace the nozzles or ports 6 are provided through which secondary air is admitted into the combustion chamber the air bein led to these nozzles by means of the conduit Additional secondary air isad-mitted into the combustion chamber through nozzles or'ports 8 in the rear wall of the furnace, the air being led thereto by means of a conduit 9. By way of example the velocity of the air admitted at these points is sutficiently high so that the air jets will penetrate well into the flame massj Velocities as high as 100 feet per second or more are contemplated.

The conduits 4, 7 and 9 are in communication with a common conduit 10 having branches 10* and sub-branches 10 through the medium of which the air, preferably preheated, is supplied to these conduits.

ing to transport the coal to the burners may also be supplied from the conduit 10 through the medium of the branch conduit 11.

In this connection it 1s pointed out that the air serv- An air preheater 12 is located in the stack 13 of the furnace, through which preheater air is passed by means of a forced draft fan.

14, preferably of variable speed. The air leaving the preheater 12 enters the conduit 10 hereinbefore mentioned. It will thus be seen that all of the. air for combustion may be supplied by a single fan.

In order to regulate the velocity and volume of the air admitted at the various points above described, dampers 15, 16, 17 and 18 for regulating the flow of air through the conduits 4, 7 9 and 11, respectively, are provided. Regulation of the dam ers permits the creation of any desired egree of ciation with adjustment of the dampers.

Reverting now to the burner means C and the air nozzles 6 and 8, it will be seen that they are so disposed with relation to one another that the air streams emitted therefrom are approximately tangent to an imaginary cylinder within the combustion chamber, the axis of which is horizontal and parallel to the front wall of the furnace. In the particular arrangement shown the burners C are located in the arch 19 and toward the front wall a of the furnace; the nozzles 6 are located well toward the bottom of the front wall, and the air nozzles 8 are located in the rear wall e at a level higher than the level of the nozzles 6. In this instance the burners are shown inclined somewhat from the vertical and the air nozzles 1n horizontal until it meets the air barrage set up at f by the nozzles 6. On entering this barrage the fuel and flame stream is turned and then rises under the influence of the draft and is met at g by the air supplied by the nozzles 8. As

the fuel and flame stream encounters the air admitted through nozzles 6, turbulence is.

created and this turbulence is continued and added to by the air admitted by the nozzles 8. The flame, considered as a whole, takes the general course indicated, with the forma-= tion of'many local eddies, and the throat portion is practically filled with the products of combustion. The two streams of air have a tendency to cause a whirling motion of the -main body of the flame about a horizontal axis. Thus, intense turbulence with intense combustion isobtained within the furnace.

. By reason of the flame stream being turned as above mentioned it is prevented under regular operating conditions from penetrating behind the water screen E.

From the foregoing it will be seen that there will be a recirculation, so to speak, of the coarser particles'of coal, which tend to gravitate into the lower part of the fuel and flame stream, whereby they will be more completely burned than heretofore. That is to say, the coarsest particles of coal work toward the outside of the first portion of the fuel and flamestream, and when they reach the air streams from the nozzles 8 they will be subjected to fresh incoming oxygen-laden air, and be more completely burned. In the event that they are not completely consumed they will again be caught by theflame and so on until they are too small to be affected by the difference between their own density and that of the gases. The heavier particles very largely take the course indicated in the drawings until they are finally consumed. Thus, effective combustion is obtained with 10v. carbon losses. It is also pointed out that higher combustion rates and'higher capacities because of the high rate of heat transmission are obtained than were heretofore possible. The available combustion space is more completely utilized than heretofore which increases the time consumed by the gases and fuel in passing through a furnace, hence increasing the efficiency of combustion.

Also through the practice of the invention water wall lined combustion chambers can be used to greater advantage than heretofore.

The invention is of such nature that the capacities of existing furnaces may be increased with a minimum of expense.

In Fig. 2 a convenient arrangement is shown for inserting the air nozzles between finned tubes of a water wall lined combustion chamber without altering the spacing of the tubes.

While the air is described asbeing pre heated by means of an air heater located in the stack, it will be understood that in some instances it may be desirable. to heat the air in the hollows of hollow furnace walls and pass it therefrom to the various points of introduction,

I claim In combination, a substantially unobstructed combustion chamber having an outlet at the top, said chamber being of approximately rectangular cross section and of a.

volume'suflicient to ermit of the combustion substantially horizontal direction at a level approximately at the bottom ofthe turn in the flame stream, and means for supplying a current of air through the opposite upright wall in a substantially horizontal direction at a level approximately midway of the point of fuel admlssion and the point of admitting said first current of air, said coal and air and said currents of air having velocities such that heavier particles of fuel gravitating toward the bottom of the chamber are caused to rotate about a horizontal axis approximately midway of the combustion chamber and parallel to said two walls, without impingement on the walls of the chamber.

In testimony whereof I have hereunto signed my name.

MARTIN FRISCH. 

